Hello,
In GnuRadio when I create some basic RTL-SDR receiver followed by FFT block I can set receiver signal frequency of my local FM station 107.5MHz and sampling frequency of 32kHz.
With that settings I can correctly see on FFT display signal of my local station. But according to Nyquist–Shannon sampling theorem, sampling rate should be at least 2 times higher than signal frequency, so in my situation I should set at least 215MHz into sampling rate parameter.
Why does it work correctly?